Posted
by
timothy
on Thursday February 04, 2010 @09:57PM
from the can-imagine-quite-a-bit dept.

astroengine writes "After 4 years of processing the highest resolution photographs the Hubble Space Telescope could muster, we now have the highest resolution view of Pluto's surface ever produced. Most excitingly, these new observations show an active world with seasonal changes altering the dwarf planet's surface. It turns out that this far-flung world has more in common with Earth than we would have ever imagined."

True, but it was the closest thing I could find on short notice. The point is that Pluto isn't very many pixels across. Also, I think when they said "best" they were actually talking about the new images, even though they didn't show a picture.

It's not quite as simple as "the image is over-exposed." Pluto is dim and small enough to be right at the edge of telescopes' resolving power. Intensity variations across its face are even harder to detect, so it usually looks like either a fuzzy white ball or a fuzzy grey ball.

your choice, but the third graders of 2080 who have to memorize 80 planets might not be too happy with you

Once upon a time, students had to memorize only four elements (earth, air, fire, and water). Nowadays we recognize over a hundred, and there are a bunch of theoretical ones we can predict but have a hard time detecting. I don’t think “but people will have a hard time remembering them all, so we have to add arbitrary limit so that we don’t have so many” is a very good way of defining terms.

I can see a good argument for saying that the solar system contains four planets and some rubble. I can see an argument for saying that it contains over a dozen planets, probably way over. I can see a good argument for saying that it consists tens of thousands of planets. I can see a good argument for saying that “planet” is not a piece of scientific terminology and letting lay usage define it.

I can see an argument, although not a great one, for coming up with a definition that keeps the number down to a dozen, but I think the definition the IAU came up with is pretty ambiguous, since “cleared the neighbourhood around its orbit” is clearly relative, and you could define “cleared”, “neighbourhood”, and “around” in such a way that Ceres has done it (admittedly a stretch), or that Jupiter hasn’t. (There’s also the matter of “has” — do things that weren’t planets early in the history of the solar system become planets as time passes and they collect impacts?) And the IAU definition explicitly excludes anything that orbits around any star other than our sun, which to my mind makes it just silly, and means that a sizable fraction of the astronomical community is concerned with studying planets (and publishing papers calling them planets) that do not meet the IAU definition.

Incidentally, once upon a time, any new thing discovered in orbit in the solar system other than the sun was considered a planet, so the moon, the moons of Jupiter, and the asteroids (the few then known) would all have been considered planets. If you exclude dust particles and the like, that’s still a reasonable definition for the sorts of things that “planetary scientists” study, and personally I kind of like that approach.

The data rate from Pluto is expected to be 1000 bits per second. It would take over two years to transfer the entire 8GB buffer at that speed. Granted, New Horizons could send back a 1MB picture in about two hours. But the mission planners have other plans for the immediate flyby. They are going send radio signals from Earth to New Horizons to measure Doppler shift (inferring the gravitational pull and mass of Pluto) and to detect the effect Pluto's atmosphere has on the signal.

Compressed pictures should be available to the public a few days after the flyby. They are expecting the full data set to take nine months.

So for decent pictures you had best revise your estimate:

Five more years until we have a GOOD picture of Pluto. July 14, 2015...can't wait!

this is funny because the word "planet" comes from the Greek word "planitis" which means "wanderer". From wikipedia:

In ancient times, astronomers noted how certain lights moved across the sky in relation to the other stars. Ancient Greeks called these planetes asteres: wandering stars or simply planetoi: wanderers, from which today's word "planet" was derived.

Now you want to change the definition of what a "planet" is while the actual meaning of the word hasn't changed. Imagine "planets" were called "wanderer stars" and then I told you that the definition of a "wanderer star" has nothing to do with movement but with size and whether the object produces hydrogen. So stop calling it "wanderer star" then!

I checked a number of sources and it put it at 0.14% of the crust, and about 0% of the mantle and core. The crust is about 0.015% of the volume of the Earth (and less than that by mass). Multiply it out, you get 0.0021%. My bad for forgetting the oceans. Still, it's really a negligible percentage either way.

The classification of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun.[17] Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno and 4 Vesta) for about half a century until further asteroids were discovered.[17][25][35]However, as other objects were discovered in the area it was realised that Ceres represented the first of a class of many similar bodies.[17] In 1802 Sir William Herschel coined the term asteroid ("star-like") for such bodies,[35] writing "they resemble small stars so much as hardly to be distinguished from them, even by very good telescopes".[36] As the first such body to be discovered, it was given the designation 1 Ceres under the modern system of asteroid numbering.[35]

they got over it WHEN THE NEIGHBORHOOD WAS FOUND TO BE FULL OF SUCH MIDGETS

sound familiar? when the deluge of asteroids came in, people thought "uh, its going a little crazy with these planets here, lets lop off the pretenders". now, as they search and catalog the oort cloud, they find that pluto's experience is like ceres's experience in the asteroid belt: planet, until the deluge of neighbors, then demotion. its happened before, its happening again. there's no claim to pluto's status except nostalgia. they got over it in the 1800s, you can get over it now

pluto was discovered in in 1930, and kicked out of the club in 2006. that's a nice 75 year run, 50% more time than ceres

the only thing you have going for your clinging to pluto is adherence to tradition. that's not a good reason to say everything and its uncle is a planet, just to preserve pluto's status. its far easier to lop off pluto, consider us to have 4 (rocky) +4 (gas) planets, and be done with it. everything else is dwarf planet/ comet/ asteroid/ etc.: detritus, flotsam and jetsam, left over rocks, of lower import than the main 8